przemratajczak/mangos — comment on commit b6c69c5ed1573d854b550b076e9c4687a571ac58
File:  line 0
By michalpolko:

this doesnt seem correct to what i found and have seen on youtube.
damage increases twice every next stack plus some additional amount.
until then this formula might do the trick ;p

and yes, 2 tanks with 3 stacks deal less damage than 1 tank with 5 stacks ;]